If you are afraid of investing, there's a chance you have a decent chunk of change saved in a checking or savings account. Saving money is always a good thing.
Angel investing is a high-risk, high-reward proposition. Angel investing also provides a path to equity ownership in an eventual global company's infantile stages.
Utilizing your real estate is a great way to turn your property into rental income. You don't have to buy a rental property, use what you already own!
If you have a second car sitting around or have begun to bike to work and no longer need the vehicle daily, this might be the perfect way to start generating some passive income.
Some websites sell digital products. But most common is to rely on advertising revenue as their primary source of building a passive income.